☆they give evidence of types of plants/animals that existed at certain geological age/long
ago/millions of years ago
☆gives evidence of morphological/anatomical/structural changes that have taken place over a
long period of time e. g. human skull, leg of horse
ii) Comparative anatomy
☆gives evidence of relationship among organisms/gives evidence of a common ancestry of a
group of organisms
☆organisms have similar structures/organs performing the same function e. g. digestive system]
urinary system/nervous system/vestigial structures and vertebrate heart
☆Divergence where the basic structural form is modified to serve different functions e.g.
vertebrate forelimb/beak structure in birds/birds feet/parts of a flower. These are called
homologous structures
☆homologous structures have a common embryonic origin but are modified to perform different
functions e.g. the pentadactyl .
☆adaptive radiation is a situation where organism have a homologous structure with common
embryonic origin which is modified to perform different functions to adapt organisms to
different ecological niches/habitats e.g. beaks of Darwinian finches(birds)
☆Convergence is where different structures are modified to perform a similar function e.g.
wings of birds and insects/eyes of humans and octopuses. These are called analogous structures
☆Vestigial structures are greatly reduced in size and have ceased to function e.g. human
appendix/caecium/coccix in humans, wings of kiwi (flightless bird), presence of hind limb pad in
python, halters in insects, human hair nictitating membrane in human eye, human ear muscle,
pelvic girdle in whale and third digit of wing of bird.
iii) Comparative embryology
☆some embryos of different animals appear very similar thus showing relationship and
possibility of a common ancestry
e.g. different classes of vertebrates larvae of annelida and mollusca are similar (tocophere)
iii) Comparative serology/physiology